Ferromagnetic material



y 1960 R G. H. JONKER EIAL 2,946,752

FERROMAGNETIC MATERIAL Filed Aug. 9, 1956 2 Sheets-Sheet 1 FIG.1

IN VEN TORS GERARD HEINRICH JSJNKER HENRICUS PET RUS OHANNES WIJN POUL BERNARD BRAUN BY 97 2 K AGENT July 26, 1960 G. H. JONKER ETAL 2,946,752

FERROMAGNETIC MATERIAL Filed Aug. 9, 1956 2 Sheets-Sheet 2 IO 50 I00 FrgMc/sec.- 5OO IOOO INVENTORS GERARD HENRICH JONKER HENRICUS PETRUS JOHANNES WIJN POUL BERNARD BRAUN BY {b 7K AGENT I 2,946,752 r Y, FERROMAGNETIC MATERIAL" Gerard Heinrich Jonker, Henricns Petrus Johannes Wiin, and foul Bernard Brann, all of Eindhoven, Netherlands, assignors, by mesne assignments, to North American PhilipsCompany, Inc., New York, N.Y.', a corporation of Delaware Filed Aug. 9, 19 56, ser. No. 603,135 Claims priority, applicationiNetherlands' Aug; 10, 1955 6 Claims. (01. 252-625) Patented July 125, seen materials of our invention exhibit relatively low residual loss factors (tan at frequencies above 50 mc./s.

i The novel materials of our invention have a crystal structure of which the unit cell'in the hexagonal crystal system has a -axis of about 52.3 A and an a-axis of about5.9 A. w a a We prepare'the novel materials of'our invention by heating at a temperature of more than 1200f C. a finely bility in a certain frequency range the position of which in the frequency scale is related to the low-frequency value of the initial permeability. The initial permeability decreases in a frequency range the position of which in the frequency scale is higher in proportion as the value of the initial permeability at low-frequency is lower. Thus the cores formed from these materials are not too satisfactory for use at high frequencies.

The principal object of ourinvention, therefore, is to provide a new and novel class of oxidic ferromagnetic materials the initial permeability of which decreases in I;

a much higher positioned frequency range than in the known materials with anequal low-frequency value of the initial permeability, v V 7 Another object of our'inven'tion is to provide oxidic ferromagnetic materials which have initial permeabilities of more and often materially more than 2 at frequencies of about 50 mc./s. and often considerably higher 'frequencies and which exhibit lowvlo sses, Q r

Still another object ,of our invention is to provide oxidic ferromagnetic materials which may serve as materials for magnetic, bodies eg. cgres at'frequencies of about 5'0 mc./s. and often considerably higher frequencies. r g

These and other objects of our invention will belapparent as the specification progresses.

According to our invention Wehave found anew and novel material which is formed essentially of h'exagonal crystals containing about 17.6 mol. percent 3510', 11.8 mol. percent CoOand 79.6 mol. percent B3 0 This material may be considered to have a compcsition corresponding to the formulaBa Co Fe-go fFroni further investigations it appeared that in the aforesaid formula the Ba-ions may be replaced partly by similarfions, for example S r-, Caand Pb ions or acornbination of these V ture of the oxides.

divided mixture of metallic oxides in a ratio approximately corresponding to that of the metals in the materials or our'invention. Alternatively instead of a metallic oxide we may use a material which forms an oxide when heated. As these oxide-forming materials we may use carbonates, oxalates and acetates of the metals. Moreover, instead of metallic oxides we may use one or more preformed reaction products of at least two of the metallic oxides. e

Preferably we. prepare the novel materials of our invention by heating. to a temperature of more than .1200 C. in an. atmosphere containing at least as much; oxygen .as air, a finely divided mixture of metallic oxides and/ or oxide-forming. materials and/or reaction products of metallic oxides; in a ratio approximately corresponding to that of the metals in the materials of our invention.

As a preformed reaction product of at least two of the metallic oxides we preferably use an iron-containing reaction product, which has been produced at low temperature, preferably below 1100 C., and which has a crystal structure corresponding with that of the mineral magnetoplumbite, for exampleBa Sr Fe O wheresilicates such as pentonite or fluorides such as calcium fluoride in an amount of from 0.25% to 5% in the mix- Bodies of desired shape maybe formed by sintering the starting mixtures directly in the desired shape. Alternatively bodies of desired shape. may be formed by regrmding the sintered material of our invention, or the presintered material, molding the resultant powder into ions, i.e. for not more than one third part. The aforesaid formula may thus be restated as follows:

3 ;Ma i n t1 I inwhich M is-at least one metal selected from the group consisting of strontium, calcium, andlead, and the subs p 4 avalu l ss than T Thesem s alahav initial permeabilities which do not decrease substantial-g ly up to very high frequencies; They haveinitial per meabilities of more and often materially more than. 2. at frequencies of about 50 mc./s. and often considerably Since they are basically oxidic in nature they are characterized by high ohmic resisltancem'; so that eddy current losses are negligibly'small. 'In 'ad f dition to having greatly improvedinitialpermeabilities higher frequencies.

at high frequencies, particularly above 50 mc./s., the

the desired shape and sintering the molded product if necessary. A binder such as water, a solution of'nitrocellulose or a solution of carboxymethylcellulose may be addedto the powdered mixtures before molding if necessary. 7

In a further embodiment of our invention the finely divided material of our invention is molded to forma body of the desired shape by pressing the relative material together with a binding agent which is capable of being hardened (for example'a polyester resinor an 'ethoxylin resin), followed'by hardening the molded body.

" the values of the loss factor tan 6 to frequency for one 7 embodiment of our invention and Fig. 2 is a graph showing the relationship between the yaliiefslof the real portion of initial permeability, IL, and

" the' yalues of the loss factor tan 6 to frequency for a: jsecond embodiment of our invention.

The relationship between the loss factor tan 6 and the v. realportion of initial permeability, will-be apparent from the following explanation which forms no part of limit the scope of our invention:

The term p asused herein may be explained as 5, at a pressure of 1000 kgs./cm. having an outer diameter of about 35 mms, an inner diameter of about 25 rnms. and a height of about 4 mms. These rings were sintered for two hours at 1260 C. in oxygen. An X-ray examinafollows: A sinusoidally alternating magnetic field with 5 tion proved that the reaction product consisted Wholly small amplitude will produce a similarly varying inductof crystals with the desired structure. The properties are ance in a ferromagnetic body but due to ferromagnetic indicated in the table under N0. 4. losses there will be a phase difierence between the mag- Example V netic field and the inductance. Thus the permeability of the ferromagnetic body, ,u, may be represented by a com- 10 i PQ 12 19 was p l Produced y Plex magnitude m" The real portion f permsheatmg a mixture of BaCO and 'Fe O 1n the correct ability, o, is in phase with the field applied while the mtlo at 1000 for 15 h0l1r$- f' W1th BaCO3 other lags in phase by 90 with respect to the applied and Cocoa 11118 Product Was mlXed In the ratio 2 field. The loss factor tan 6 can then be defined as mols 12 19 1 1110133003 and 2 H1015 Cocoa, Winch 15 corresponds'to the desired formula Ba Co Fe O The tan mixture was ground with alcohol in a vibration mill for n 4 hours. Rings were molded from this product at a Example 1 pressure of 1000 kgs/cmP; these rings were fired for one hour at 1270 C. in oxygen. X-ray examination 3 i s i f 3 63 of BaCO3vd19f7-5 of F3203 proved that the reaction product cons1sted wholly of crysan 8 0 a was E a an our tals with the desired structure. The to erties of the with ethyl alcohol in a porcelain ball mill. Subsequent rings a indicated in the table under 5 5? to drying the oxide mixture was heated for 15 hours 1 l in air at a temperature of about 1000 C. The reaction Exam? 8 VI product was ground again for half an hour. Then rings 25 Th compound Ba gSr Fe O was previously prowere molded therefrom at a pressure of 1000 kgs./cm. du d by heating a ixture of BaCO srco and Fe O these rings having an outer diameter of about 35 mms. in the correct ratio for 15 hours at 1000 C. Together and an inner diameter of about ZS'mrns. and a height with B CO and CoCO this product was mixed in a of about 4 mms. These rings were sintered for one ratio of 2, mol Ba Sr Fe O '1 mol BaCQ and 2 110111 in Oxygen at a temperature C. The P P- mols CoCO which corresponds to the desired compound erties of these sintered rings are indicated in the table B s c Fe o Th ixtur was.gr0u11d fo 4 under N0. 1. hours with alcohol in a vibration mill. Rings were mold- Example 1 ed from this product at a pressure of 1000 kgs./cm. From a mixture of 627 of Bacoa 200 of F6203 these rmgs were fired for one hour at 1260 C. 111 oxygen. and 21.3 of COCOSI rings were molded at a Pressure X-ray exarmnationproved that the reaction product conof 1000 kgs./cm. these rings were sintered as in the sisted of i f' Structure The Proper manner described in Example L The Properties of the ties of the rings are indicated in the table under N0. 6. sintered rings are indicated in the table under N0. 2. Example VII Example Ill 40 a e A mixture of cobalt carbonate barium carbonate and A mixture of 23.0 gs. of BaCO 72.5 gs. of Fe O and 795 gs. of Cocoa was ground for half an hour with ferric oxide in a ratio in accordance w th the formula Ba Co Fe O was ground for 15 hours wlth ethyl alcohol ethyl alcohol in a porcelain ball mill. The dried mixture in an 11'011 ball 111111. The dried mixture was smtered was heated for 15 hours 1n air at 1000 C. and then f h C d h round again for half an hour. The Powder obtained 45 or two olirs at an t e r-eactlon Product w a ground again for 15 hours. The dr-led powder was smwas heated for one hour 1n oxygen at 1200 C. a This t o ered again for two hours at 1200 C. m a stream of reaction product was reground for one hour. From the oxygen. Thls sintered material was finely ground with powder, rings were molded at a pressure of 1000 kgs./

2 ethyl alcohol in a vibration mlll and then drled. From cm. after the addition of a small quantity of a solution this owder fin S were m 01 de d at e a ressure of 200 of nitro-celluloseas an organic binder. These rings were k p 2 g p I o gs./cm. after the addition of a small quantity of a then heated in oxygen at 1275 C. for three hours, cooled a u a solution of Araldlte in aceton as an ethoxylin resin, to 1200 C., kept at this temperature for one hour and o which were heated for eight hours at 130 C. These then cooled to room temperature within 4 hours. The 7 properties of these rings are indicated in the table under Imgs had at a f-requency 9f 260 mcjs a M of No 3 In the followlng table, in column 2, under the heading Exam le IV of Main Constituent? chemical formulae are indicated, p which were derived from the compositions of the starting A mixture of 98.7 gs. of BaCO 326.6 gs. of Fe O -rnixtures and from the X-ray examinations. All measurand 43.3 gs. of CoCO (with 45.4% by weight of Co) mg results were obtained by carrying out measurements Lia; gI 1)111ndT0ld1 (IiIOUI StWITh ethyl 11 alcglol 1n anhiron Z51 ringsh 11(11 231 demlagcrlieglz i it/late at 3001; templegatgre by a m1 e r1e mix we was eate or two ours e met 0 escri e y van er urgt, evers at 1050 C. and the reaction product was ground. again and H. P. J. Wijn in Philips Technical Review, 14, 245 for 16 hours. From the dried powder rings were molded (1952-1953).

TABLE No. Main Constituent d p n low n" Fig.

7 r 2cm frequency 50 me/s. 500 male.

Bfl3CO2Feg401 4.5 10 12 10 BasCOzFeuOn..- 4.1 10 6 10 9 11 l BasCO1Fe:4O4 4.1 10 7 7 7 BazCozFeuOu.-- 21 19 15 2 E350F6441.-.. 9. 5 9. 5 9. 6 l uiii 8.9 V 8.2 8.9

aeaavsa The graph of Fig. 1 shows the relationship between the real portion of the initial permeabi.lty, ,u', and tan 6 to frequency for the product of Example II. In this graph the values of ,u, and tan 6 are plotted along the ordinates and the values of the frequencies are plotted along the abscissa.

The graph of Fig. 2 in the same manner shows the relationship between the real portion of the initial permer ability, l, and tan 6 to Example IV. I

While we have described our invention in with specific embodiments and applications, other modifrequency for the productof fications thereof Will be readily apparent tothose skilled 7' in this art without departing from the spirit and scope of the invention as defined in the appended claims;

What is claimed is: 1. A ferromagnetic material consisting essentially of crystals of a composition having the formula v I-a a 2 24 41 in which M is a metal selected from the group consisting of strontium, calcium, and lead, and a has a value less than 1, said compound containingas the equivalent a total of 17.6 mol. percent of barium, strontium, calcium and lead oxides, 11.8 mol. percent of C00 and 70.6 mol.

percent of Fe 0 ,saidcrysta1s having a structure, the;

unit cell of which in the hexagonal cry'stal system has a c-axis. of about 52.3 Aand an 'a-axis of about 5.9 A.

2. 'A ferromagnetic body having an'initial permeability of at least 2 at frequencies of at least 50 mc./sec. conof a composition having the formula:

3-a a 2 Z4 4I in which M is a metal selected from the group consisting of strontium, calcium, and lead and a has a value less than 1, said crystals having a structure, the unit cell of which in the hexagonal system has a c-axis of 52.3 A and an a-axis of about 5.9 A. p

3. A method of producing a ferromagnetic material comprising the steps, forming a finely-divided mixture of oxides in proportions forming upon sintering crystals of a composition having the formula:

in which M is a metal selected from the group consisting of calcium, strontium, and lead and a has a value less than 1, said crystals having a structure, the unit cell of which in the hexagonal crystal system has a c-axis of 52.3 A and an a-axis of about 5.9 A; and heating said mixture to a temperature of at least 1200 C. in an atmosphere containing at least as much oxygen as air for a time sufficient to form the crystals.

4. A method of producing a-ferromagnetic material comprising the steps, forming a finely-divided mixture of oxides of divalent metals and ferric oxide in propor tions forming upon heatingcrystals having a structure so. sisting essentially of a highly coherent mass of crystals correspondingtothe mineral; magnetoplumbite; heat-j ing said mixture. to a temperaturebelow ,1100 C; but

suflicient to form said crystals; mixing said crystals with oxides forming therewith upon heating crystals of a composition having the formula V aMac irea in which M is a metal selected from the group consisting of strontium, calcium, and lead and a has a value less 10' connectlon than 1, said latter crystals having a structure, the unit cell of which in the hexagonal crystal system has a c-ams of about 52.3 A and an a-axis of about 5.9 A; heating said latter mixture to a temperature of at least 1200 C. in an atmosphere containing at least as much oxygen as air for a time suflicient' to form said latter crystals.

. 5. A method of producing a ferromagnetic material comprising the steps, forming a finely-divided mixture of oxides in proportions forming upon subsequent heating crystals of a composition having the formula:

fB sa a z zt u g in which M is a metal selected from the group consist -'-ing of strontium, calcium, and lead, and a has a value lessthan 1, said crystals having a structure, the unit 'cell of which in vthe hexagonal crystal'system has a c -axis I of about 52.3 A and an a-axis of about 5.9 A; heating 1 said mixture to a temperature of about 800 to 1100 C. to substantially react the oxides into forming said composition; finely-dividing said reaction product; and heat- I ing said finely-divided reaction product at a temperature of at least about 1200 C. in an atmosphere containing at least as much oxygen as air for a time sufficient to form said crystals. j

6. A method of making a ferromagnetic body having an initial permeability exceeding at least 2 at a frequency of at least 50 mc./sec. comprising the steps, forming a finely-divided mixture of oxides in proportions forming upon heating crystals of a composition having the,

formula: Ba ,,M,,Co Fe O in which M is a metal selected from the group consisting of strontium, calcium and lead and a has a value less than 1, said crystals having a structure, the unit cell of which in the hexagonal crystal system has a c-axis of about 52.3 A and an a-axis of about 5.9 A; compacting said mixture into a body of desired shape and dimensions; and heating said body to a temperature of at least 1200 C. inan atmosphere containing at least as much oxygen as air for a time sufiicient' to form said crystals.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Erchalkfet 211.: I. Amer.Chem. Soc., October-1 1946,

Harvey et' al.: RCA Review;September 1, 1950,'p. 346. "Phillips Technical Review, vol.. 13, N0. .77, pp. 194-208. A 4 i Phillips-Technical Reviewf' vol.18,N A 154. I y i 

1. A FERROMAGNETIC METAL CONSISTING ESSENTIALLY OF CRYSTALS OF A COMPOSITION HAVING THE FORMULA 